1. Field of the Invention
The present invention relates generally to a motor controlling method and an apparatus, and more particularly to controlling technology for a stepping motor applied to a panhead driving part of a camera or the like.
2. Description of Related Art
Conventionally, in case of a driving part using a stepping motor, operation curved lines of acceleration and deceleration showing the relationship between the movement amount of a panhead and the time are quadratic curves. An operation curved line showing the relationship between the speed and the time is shaped like a trapezoid as shown in FIG. 5 (Japanese Patent No. 2810934).
However, the panhead can not be moved at a high speed at the beginning of the operation since the torque of the stepping motor is low at the beginning. Also, in the conventional controlling method, the panhead can not be smoothly moved since the acceleration of the panhead is rapidly changed when the panhead is shifted from the acceleration to constant-speed-movement and from the constant-speed-movement to the deceleration.
It is therefore an object of the present invention to provide a stepping motor controlling method and apparatus in which a movable object can be smoothly shifted from acceleration to constant-speed-movement and from the constant-speed-movement to deceleration when the movable object is moved to a designated position in a designated time.
To achieve the above-described object, the present invention is directed to a motor controlling method for moving a movable object with a motor to a target position in a designated time, comprising the steps of: determining an acceleration period, a constant-speed-movement period and a deceleration period according to at least one of the target position and the designated time; applying exponential functions to operation equations of the acceleration and the deceleration showing relationships between movement amounts and a time; determining a constant speed during the constant-speed-movement and the exponential functions so that said movable object is smoothly shifted from the acceleration to the constant-speed-movement and from the constant-speed-movement to the deceleration; and driving said motor according to the determined exponential functions.
According to this invention, the exponential functions are applied to the operation equations of the acceleration and the constant-speed-movement, and the operation equations are determined so that the movable object is smoothly shifted from the acceleration to the constant-speed-movement and from the constant-speed-movement to the deceleration. Therefore, the movable object can be smoothly moved over the whole operation.
To achieve the above-described object, the present invention is directed to a motor controlling method, comprising the steps of: inputting a target position for a movable object; inputting a time for said movable object to arrive at the target position; determining an acceleration period, a constant-speed-movement period and a deceleration period according to one of the inputted target position and time; setting a constant-speed-movement start position at which the constant-speed-movement is started; setting a deceleration start position at which the deceleration is started; determining a constant speed during the constant-speed-movement according to the set constant-speed-movement start position and deceleration start position; applying an exponential function to an operation equation of the acceleration showing a relationship between a movement amount and a time and determining the operation equation so that the speed when said movable object is shifted from the acceleration to the constant-speed-movement is the same as the determined constant speed; applying an exponential function to an operation equation of the deceleration showing a relationship between a movement amount and a time and determining the operation equation so that the speed when said movable object is shifted from the constant-speed-movement to the deceleration is the same as the determined constant speed; and driving a motor to move said movable object to the target position according to the determined operation equation of the acceleration, constant speed during the constant-speed-movement and operation equation of the deceleration.
To achieve the above-described object, the present invention is directed to a motor controlling apparatus comprising: a target position inputting device that inputs a target position for a movable object; a time inputting device that inputs a time for said movable object to arrive at the target position; a period setting device that determines an acceleration period, a constant-speed-movement period and a deceleration period according to one of the inputted target position and time; a constant-speed-movement start position setting device that sets a constant-speed-movement start position at which the constant-speed-movement is started; a deceleration start position setting device that sets a deceleration start position at which the deceleration is started; a constant speed determining device that determines a constant speed during the constant-speed-movement according to the set constant-speed-movement start position and deceleration start position; an operation equation determining device that applies an exponential function to an operation equation of the acceleration showing a relationship between a movement amount and a time and determines the operation equation so that the speed when said movable object is shifted from the acceleration to the constant-speed-movement is the same as the determined constant speed, and applies an exponential function to an operation equation of the deceleration showing a relationship between a movement amount and a time and determines the operation equation so that the speed when said movable object is shifted from the constant-speed-movement to the deceleration is the same as the determined constant speed; and a control signal generating device that drives a motor to move said movable object to the target position according to the determined operation equation of the acceleration, constant speed during the constant-speed-movement and operation equation of the deceleration.
To achieve the above-described object, the present invention is directed to a recording medium that stores a program for executing the steps of, with a computer: designating a target position for a movable object and inputting a target position to said computer; designating a time for said movable object to arrive at the target position and inputting the time to said computer; determining an acceleration period, a constant-speed-movement period and a deceleration period according to one of the inputted target position and time and inputting the acceleration period, the constant-speed-movement period and the deceleration period to said computer; setting a constant-speed-movement start position at which the constant-speed-movement is started and inputting the constant-speed-movement start position to said computer; setting a deceleration start position at which the deceleration is started and inputting the deceleration start position to said computer; finding a constant speed during the constant-speed-movement according to the set constant-speed-movement start position and deceleration start position; and applying an exponential function to an operation equation of the acceleration showing a relationship between a movement amount and a time and calculating for determining the operation equation so that the speed when said movable object is shifted from the acceleration to the constant-speed-movement is the same as the determined constant speed, and applying an exponential function to an operation equation of the deceleration showing a relationship between a movement amount and a time and calculating for determining the operation equation so that the speed when said movable object is shifted from the constant-speed-movement to the deceleration is the same as the determined constant speed.
The recording medium may be a read only memory (ROM) loaded in the apparatus, and it may be an outer recording medium such as a floppy disc, a photo-magnetic disc and an IC memory card.